Variable Focus Microlens

ABSTRACT

A microlens chip comprises a variable focus fluidic microlens and actuator. The actuator varies the pressure in a fluidic channel in the microlens chip which is coupled to an aperture opening containing the microlens. Applying an electric field to the actuator creates changes in fluid pressure in the fluidic channel, which in turn changes the radius of curvature (i.e., focal length) of the fluidic microlens.

FIELD OF THE INVENTION

This invention relates to microlenses in general. More particularly, theinvention relates to variable focus liquid microlenses.

BACKGROUND OF THE INVENTION

FIG. 1 shows a conventional fluidic microlens 101. As shown, themicrolens comprises a substrate 110. The substrate includes a groundelectrode 121 between first and second control electrodes 123 a-b. Theground electrode is coupled to ground reference voltage while thecontrol electrodes are coupled to variable voltage sources. Dielectricand coating layers 130 and 135 are disposed over the electrodes. Thecoating layer comprises a hydrophobic material, such aspolytetrafluoroethylene (e.g., Teflon). The dielectric and coatinglayers are patterned to create a window 139, exposing the groundelectrode.

A drop of conductive liquid 140 is disposed on the coating layer. Thedrop serves as the microlens. The drop contacts the surface and groundelectrode. In an inactive stage, (no voltage applied to the controlelectrodes), the drop takes on a first shape, as designated by the solidline 141. This shape depends on the size of the drop and the surfaceenergy of the hydrophobic coating layer. When a voltage is applied tothe control electrodes, the electric potential from the voltage causesthe hydrophobic coating layer to become hydrophilic (e.g., change inwettability), thereby changing the curvature of the drop, as designatedby the dotted line 142. The change in curvature changes the focallength. Changing the wettability of the coating layer using an electricfield to change the focal length of the fluidic microlens is known as“electrowetting”.

However, various problems are associated with electrowetting-controlledfluidic microlenses, limiting their performance. Such problems, forexample, include liquid evaporation, contact angle hysteresis, low focallength tunability and high driving voltages. Additionally, the surfaceenergy of the hydrophobic layer creates discrete rapid jumps incurvature change of the microlens instead of a smooth continuous one.This is referred to as the stick-slip behaviour.

Therefore, in view of the foregoing discussion, it is desirable toprovide an improved microlens which avoids the problems associated withconventional microlens.

SUMMARY OF THE INVENTION

The invention generally relates to microlenses. In one embodiment, theinvention relates to a variable focus microlens. The microlens, forexample, is incorporated into a microlens package, forming a microlenschip. The package includes a top surface having an aperture opening. Theaperture opening is coupled to a fluidic channel formed in the package.The fluidic channel is filled with a fluid, which is used to form amicrolens at the aperture opening. An actuator, such as a pump,generates fluid pressure in the fluidic channel for focusing the fluidicmicrolens at the aperture opening.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a conventional liquid microlens;

FIG. 2 shows a cross-sectional view of a microlens in accordance withone embodiment of the invention;

FIGS. 3-9 show cross-sectional views of microlenses in accordance withother embodiments of the invention;

FIGS. 10-13 show top views of actuators in accordance with variousembodiments of the invention;

FIGS. 14 a-b show top and cross-sectional views of a microlens inaccordance with one embodiment of the invention; and

FIGS. 15 a-b show cross-sectional views of a microlens in accordancewith various embodiments.

PREFERRED EMBODIMENTS OF THE INVENTION

The present invention relates generally to fluidic microlenses. In oneembodiment, the fluidic microlens is incorporated in amicro-electromechanical system (MEMS), to form a microlens chip. Themicrolens chip integrates both the lens and actuator. The microlens chipis conducive to micromachining processes. In accordance with oneembodiment of the invention, actuation of the fluidic microlens(including formation and focusing) is achieved by changing fluidpressure. Other techniques for actuating the microlens are also useful.

FIG. 2 shows a cross-sectional view of a microlens chip 201 inaccordance with one embodiment of the invention. As shown, the microlenschip comprises a package 206. Various materials can be used to form thepackage. For example, the package can be formed from glass, quartz,polymer, ceramic or a combination thereof. Other materials can also beuseful. In one embodiment, the package is substantially rigid. Providinga flexible package is also useful.

The package comprises a top surface 209. The top surface includes anaperture opening 239. The aperture opening serves to contain or supporta liquid microlens. The top surface, in one embodiment, comprises ahydrophobic material. For example, the hydrophobic material comprises apolymer. Polymers, such as polyimide, polydimethyl-siloxane (PDMS),polymethyl methacrylate (PMMA), polycarbonate, Nylon, or Teflon are alsouseful. Other types of materials can also be useful.

The lens aperture opening comprises, for example, a circular shape. Thediameter of the opening is between about 5 um to 5 mm. Other dimensionsmay also be useful. Providing an aperture opening having shapes otherthan a circular shape is also useful. For example, the aperture cancomprise an elliptical, square, or rectangular shape. Other geometricshapes could also be useful, depending on the application. The lensaperture, for example, is used to form a spherical or cylindricalshaped-like lens. Providing a lens aperture for forming other types oflenses is also useful.

Within the package is a fluidic channel 240 in communication with thelens aperture. The fluidic channel is filled with a fluid used forforming a liquid microlens 241 at the lens aperture. In one embodiment,the fluid comprises a transparent fluid. The surface tension of thefluid should be sufficient for forming the liquid lens. Preferably, thefluid has a high surface tension. The fluid should preferably comprise ahigh refractive index about, for example, 1.3 to 1.75. Fluids havingother refractive indices are also useful. Preferably, the fluidcomprises a polar liquid, such as water or polyhydric alcohols. Asshown, the fluidic channel runs along the length of the package, asindicated by arrow L. Other configurations of the fluidic channel (e.g.,different directions) are also useful.

In one embodiment, at least the bottom surface 208 of the package in thearea corresponding to the lens aperture is transparent to allow lightthrough. Preferably, the bottom surface of the package in the areas notcorresponding to the lens aperture is non-transparent to minimizeadverse effects of light reflections. The package can be formed fromvarious types of materials, such as glass, quartz, or polymer. Thematerials used in forming the package can also be transparent,non-transparent materials or a combination thereof. Additionally, thepackage can be formed from more than one portion, such as top, bottom ormultiple portions.

For a package formed from transparent or a combination of transparentand non-transparent materials, one or more opaque layers can be formedover the package, patterned as necessary to leave a transparent area asdesired. Where the bottom surface or portion of the package is formedfrom a non-transparent material, a window can be created by removing thenon-transparent material in the area of the bottom surface correspondingto the lens aperture. The window can be covered by a transparent layerto seal the window. Alternatively, a transparent cover can be attachedto the bottom surface to seal the window. In yet another embodiment, thewindow is left uncovered to form a second lens aperture.

A lens actuator 245 is provided in the package. The lens actuator is incommunication with the fluidic channel. The lens actuator actuates theliquid microlens, including lens formation and lens focusing. In oneembodiment, the lens actuator actuates the liquid microlens by causingor inducing fluid to flow in the fluidic channel. More preferably, thelens actuator actuates the liquid microlens by controlling the amount ofliquid flowing into the lens aperture or into the liquid lens at thelens aperture. Depending on the direction of fluid flow (e.g., away fromor toward the lens aperture), the lens can be formed or its radius ofcurvature changed (e.g., increased or decreased).

Various techniques can be employed to cause or induce fluid flow in thefluidic channel or fluid flowing into or out of the lens. For example, apump can be used to cause fluid flow while a volume change in thefluidic channel (or a fluid reservoir in communication with the fluidicchannel) induces fluid flow. Providing an actuator that employs acombination of fluid flow techniques or a plurality of actuators is alsouseful. Alternatively, pressure outside the fluidic channel can becontrolled to cause fluid flow within the channel. For example, pressureinside the fluidic channel can be maintained to form a lens whilepressure outside (e.g., outside the lens aperture) can be varied toincrease or decrease the amount of fluid flowing into the lens to varyits curvature. Changing the curvature of the lens changes its focallength.

In one embodiment, fluid flow corresponds to a pressure change in thefluidic channel. For example, an increase in pressure correlates withthe fluid flowing in a first direction while a decrease in pressurecorrelates with the fluid flowing in a second direction.

The focal length (f) of a fluidic spherical lens, in one embodiment, isinversely proportional to the internal fluid pressure (P) and directlyproportional to the surface tension of the liquid (σ) in accordance withthe following equation: $f = \frac{2\quad\sigma}{\Delta\quad n\quad P}$where Δn is the difference in refractive indices between liquid and air.Being able to vary the focal length using the electrically controlledlens actuator allows the microlens to have a very compact design. Inaddition, the control of the focusing mechanism using internal fluidpressure allows for continuous, real-time and precise focusing, withwider focal length tunability.

To actuate the microlens, a voltage is applied to the electrodes of thelens actuator. Applying a voltage to the electrodes creates anelectrical potential to activate the actuator. Depending on the bias ofthe electrical potential, the fluid flows in a first direction towardsthe aperture (arrow 280) or in a second direction away from the aperture(arrow 281).

The fluid flow generated changes the internal fluid pressure in thechannel. This affects the curvature of the lens, which in turn affectsthe focal length of the lens. For example, in the absence of anelectrical bias, the lens curvature may take the shape, as indicated byline 241 a. The initial shape can be convex or concave, depending on thetype of fluid used. As a positive bias is applied to the electrodes tocause the fluid to flow towards the direction of the aperture, internalfluid pressure is increased. This causes a decrease in the lens radiusof curvature, as indicated by dotted line 241 b. The change in curvatureis the result of pressure balance across the lens surface, as definedby:P _(int) =P _(ext) +P _(st),where P_(int) is the internal pressure of the fluid, Pst is the pressuredue to surface tension and P_(ext) is the external pressure.

Increasing the positive electrical bias further decreases the lensradius of curvature, as indicated by dotted line 241 c. Conversely,reducing the electrical bias increases the lens radius of curvature, forexample, to the point indicated by lines 241 b or 241 a, depending onthe amount of electrical bias. A concave lens shape, as indicated bydotted line 241 d, can also be achieved by further controlling the flowof the fluid away from the lens aperture.

In one embodiment, the lens actuator comprises an electricallycontrolled lens actuator. The amount and direction of fluid flow can becontrolled by applying different magnitude and polarity of voltage orcurrent. Other techniques for actuation control are also useful. Forexample, actuators that are controlled by thermal (e.g.,thermal-pneumatic), magnetic (e.g., magnetohydrodynamic), optical (e.g.,photostrictive), electrowetting pump, electromechanical (e.g.,piezoelectric) techniques or a combination thereof are also useful.

In one embodiment, the lens actuator comprises an electrokinetic pump tocontrol the direction of fluid flow. An electrokinetic pump controls thedirection of flow by the application of electrical potential. In oneembodiment, the electrokinetic pump comprises an electroosmotic pump.Other types of actuators that can control fluid flow are also useful.For example, in other embodiments, fluid flow can be controlled by usingan electromechanical lens actuator that changes shape depending on theelectrical potential applied. Other techniques or combination oftechniques for changing direction of fluid flow are also useful.

In one embodiment, a control unit is provided to control the actuator.In one embodiment, the control unit is coupled to the electrodes toregulate the electric field to the actuator by controlling the voltageapplied to the electrodes. As a result, the control unit controls thecurvature or focal length of the lens. The control unit may beintegrated into the microlens chip unit. The control unit comprises, forexample, an imaging system which has closed-loop/autofocus or anopen-loop control. In closed-loop control or autofocus, an image isprovided and the imaging system will calculate the degree to vary thefocusing of the lens. The imaging system sends an actuation signal(electrical signal) to the microlens chip unit in order to maintain afocused (sharp) image automatically. In open-loop control, manualcontrol is incorporated to manually focus the lens. Providing a controlsystem which has both open and closed-loop controls is also useful.

In one embodiment, an inlet and an outlet (not shown) are provided tofacilitate filling and flushing fluid from the lens package. Providingmore than one inlet and outlet is also useful. The inlet and outlet arein communication with the fluidic channel. The locations of the inletand outlet should be selected to facilitate filling and flushing of thesystem. Flushing of the system allows new fluid to be filled in thefluidic channel. In one embodiment, the inlet is located toward a firstend of the channel while the outlet is located toward a second end ofthe channel. Preferably, the outlet is located toward the end of thechannel near the lens aperture while the inlet is located toward the endwhere the reservoir is located. Locating the inlet and outlet atdifferent locations of the package is also useful. For non-sealedsystems, the lens aperture may serve as the outlet.

A fluid reservoir (not shown) can be provided in communication with thefluidic channel. The fluid reservoir, for example, can be part of orintegrated with the fluidic channel. In one embodiment, the fluidreservoir is used to facilitate the flow of fluids directed by theactuator. For example, the reservoir provides air space to enable fluidto flow in first or second directions in the fluidic channel. The lensactuator, in one embodiment, is located between the fluid reservoir andlens aperture. Locating the fluid reservoir at other parts of thefluidic channel is also useful.

In addition or in the alternative, the fluid reservoir can provideadditional storage of fluid for filling the fluidic channel. This isparticularly useful for non-sealed systems in which the fluid canevaporate from the channel through the lens aperture.

FIGS. 3-4 show cross-sectional views of microlens chips 201 inaccordance with other embodiments of the invention. The microlens chipsare similar to the microlens chip shown in FIG. 2. Like referencenumbers refer to like components of the microlens chip. Referring toFIG. 3, a transparent membrane 343 is disposed on the top surface of thepackage, covering at least the lens aperture. Providing a membrane whichcovers the whole surface, a portion of the package including the lensaperture or only the lens aperture 239 is also useful. The membranecomprises, for example, latex, silicon-based elastomers or fluoropolymerelastomers. Other transparent elastic materials are also useful.

The fluid pressure in the fluidic channel, for example, actuates thelens. The transparent membrane seals the lens aperture and deflects dueto the change in the fluid pressure. By providing a sealed system, thefluid that forms the microlens can be protected from damage orevaporation of the fluid.

Alternatively, as shown in FIG. 4, a transparent cover 443 is providedon the top surface of the package, enclosing an area covering at leastthe size of the lens aperture 239. The transparent cover comprises, forexample, glass, quartz or transparent polymer, which is attached to thepackage. Various techniques can be employed to attach the cover to thepackage. Other transparent materials as well as other techniques formounting the cover onto the package are also useful.

FIGS. 5-6 show cross-sectional views of microlens chips 201 inaccordance with other embodiments of the invention. Common referencenumbers refer to common components. Referring to FIG. 5, a package 206of the microlens chip includes a first fluidic channel 240 along alength L of the package. A lens aperture 239 is located toward a firstend of the fluidic channel. A lens actuator 245 is disposed in thepackage and in communication with the fluidic channel. A fluid reservoir558 is in communication with the fluidic channel. Preferably, theactuator is located between the fluid reservoir and lens aperture. Inone embodiment, the bottom surface of the package in an areacorresponding to the aperture opening is transparent.

In accordance with one embodiment of the invention, a lens cover 590encapsulates the top surface 209 of the package, forming a secondfluidic channel 593. The lens cover, for example, is formed from atransparent material, such as quartz or glass. Forming the lens coverwith a non-transparent material is also useful. For non-transparent lenscovers, an opening in an area corresponding to the lens aperture iscreated and sealed with a transparent material or transparent aperturecover.

The fluidic channels, in one embodiment, create a closed-loop. Forexample, the closed loop is created by coupling the first and secondfluidic channels at both sides of the actuator. In one embodiment, thefirst and second fluidic channels are coupled by the fluid reservoir.Providing an open-loop system where the first and second fluidicchannels are not in communication at both sides of the actuator is alsouseful.

In one embodiment, the first fluidic channel is filled with a firsttransparent fluid and the second fluidic channel is filled with a secondtransparent fluid. The first and second fluids are non-miscible withrespect to each other. The first fluid which forms the lens shouldcomprise a high surface tension and a high refractive index. The secondfluid preferably comprises substantially the same density as the firstfluid. The second fluid should also comprise a different refractiveindex from the first fluid. Providing fluids having different densitiesand/or the same refractive index is also useful.

Referring to FIG. 6, a lens 641 is formed by changing the internalpressure of the fluid in the first fluidic channel. For example, thepressure is increased by causing the first fluid to flow toward the lensaperture (arrow 380). This results in the lens having a convex shape, asindicated by dotted line 641 b. The change in the shape of the lenscauses the second liquid to flow in the opposite direction of the firstliquid (arrow 381).

Reducing the pressure by reversing the flow in the first fluid (arrow381) increases the radius of curvature of the lens, as indicated by, forexample, line 641 a. This causes the second fluid to flow in thedirection toward the aperture (arrow 380). Further reducing the pressurecreates, for example, a concave-shaped lens, as indicated by dotted line641 c.

In another embodiment, as shown in FIG. 7, the package 201 includesfirst and second lens apertures 239 a-b in communication with thefluidic channel 240. In one embodiment, the first and second lensapertures are located on opposite sides of the package. For example, thelens apertures are located on top and bottom surfaces of the package.Preferably, the lens aperture are concentric or in alignment with eachother. Providing lens apertures which are not concentric or in alignmentwith each other is also useful. First and second lenses are formed inthe lens apertures. Preferably, but not necessarily, the lens aperturescomprise the same shape and size. By providing first and secondapertures, first and second microlenses can be controlled by the sameactuator. For example, bi-convex or bi-concave lenses can be created atopposite surfaces.

Alternatively, a second fluidic channel 843 is in communication with oneof the lens apertures, as shown in FIG. 8. The second fluidic channelserves to contain a second fluid. The first and second fluids work in apush-pull manner (e.g., flowing in opposite directions). Providing asecond fluidic channel for each lens aperture (843 a-b) is also useful.It is, however, understood that the fluids in the second fluidicchannels need not be the same.

In other embodiments, the package can be provided with a plurality oflens apertures, sealed and/or unsealed to create a lens array. Theapertures can be controlled by a single actuator or each aperture can beassociated with its own actuator. Providing actuators that control someor groups of lenses while the other controls a single lens or othergroup of lenses is also useful. Various combinations of actuators andlens configurations are also useful. Additionally, lens apertures can beprovided on one or both surfaces. The lens apertures can be un-sealed orsealed using techniques already described.

For example, as shown in FIG. 9, the package includes first and secondisolated fluidic channels 240 a-b. Each fluidic channel is associatedwith its own actuator (245 a or 245 b) and lens aperture (239 a or 239b). In one embodiment, the lens apertures are located on oppositesurfaces and are concentric or in alignment with each other. Providinglens apertures which are not concentric is also useful. The lensapertures, although preferable, need not be the same size or shape.Associating an actuator with each lens aperture, various combination oflens can be formed. For example, one can be concave while the other canbe convex.

FIGS. 10-13 show top views of microlens chips 201 in accordance withdifferent embodiments of the invention. Common reference numbers referto common components. Referring to FIG. 10, a package 206 of themicrolens chip includes a fluidic channel 240 along a length L of thepackage. A lens aperture 239 is located toward a first end of thefluidic channel. An electrically controlled lens actuator 245 isdisposed in communication with the fluidic channel.

In one embodiment, the lens actuator comprises at least oneelectrokinetic pump. As shown, the lens actuator comprises first, secondand third electrokinetic pumps 546 a-c arranged in series along thefluidic channel. Other pump arrangements, such as parallel or acombination of series and parallel are also useful. First and secondelectrodes (not shown) are provided for each pump to generate anelectrical field. Providing first and second electrodes which controlmore than one pump is also useful. For example, the first and secondelectrodes can be located at respective ends of the pump arrangement forcontrolling the three pumps. By applying an electric field, the pumpcauses fluid to move in the fluidic channel. Depending on the directionof movement, the fluid pressure in the channel can be increased ordecreased.

The electrokinetic pump, for example, comprises an electroosmotic pump.Other types of electrokinetic pumps are also useful. Electroosmoticpumps are described in, for example, Goodson et al., “ElectroosmoticMicrochannel Cooling System” (US Patent Application Publication No. US2003/0062149), which is herein incorporated by reference for allpurposes. For electroosmotic pump applications, the fluid in the fluidicchannel comprises a dielectric or polar fluid.

Since the electroosmotic pump uses an electric field to drive charges inthe vicinity of the liquid-solid interface, the fluidic channelpreferably has a very high surface area to volume ratio to increase theflow rate and pressure. In one embodiment, the electroosmotic pumpcomprises a plurality of micro-channels 548 in the fluidic channel toincrease the surface area in contact with the liquid and hence enhancethe electroosmotic pumping efficiency.

In one embodiment, the micro-channels are provided by a plurality ofmicrostructures. The pumping efficiency may be increased by increasingthe number of microstructures. Groups of microstructures can also beprovided at different locations in the fluidic channel to increase thesurface area. Each group, for example, forms a pump. Providing groupsthat form a pump is also useful. Other types of configurations orgeometries of micro-channels are also useful. Additionally, sinteredmicroporous media, porous silica, nanostructured media, micro-channelplate structures, porous ceramic/polymer materials or other materialswith high surface area to volume ratio may be used to fabricate thefluidic channel so as to further increase the pumping efficiency.

When a polar liquid is brought in contact with the dielectric solid, asurface potential develops at the interface. Electroosmosis occurs whenan electric field is applied across this charged liquid-solid interface.Liquids that can be used, for example, include water, aqueous buffersolutions, electrolyte solutions of organic solvents and organicsolvent-water mixtures. Other types of liquids can also be used.

Referring to FIG. 11, the electrically controlled lens actuatorcomprises an electromechanical lens actuator 646 (e.g., a piezoelectricdisc or voice coil). Although only one electromechanical lens actuatoris shown, it is understood that providing more than one is also useful.Piezoelectric discs are described in, for example, Nguyen et al., “Afully polymeric micropump with piezoelectric actuator”, Sensors andActuators B-Chemical 97 (1): 139-145, Jan. 1, 2004; Kim J H et al., “Adisposable polydimethylsiloxane-based diffuser micropump actuated bypiezoelectric-disc”, Microelectronic Engineering 71 (2): 119-124, Feb.2004; and Nguyen et al., “Miniature valveless pumps based on printedcircuit board technique”, Sensors and Actuators A 88 (2001) 104-111, allof which are hereby incorporated by reference for all purposes. Applyingan electric field causes the electromechanical actuator to deflect,changing the pressure in the fluidic channel. This in turn controls thevolume displacement of the fluid in the channel to actuate the microlensat the lens aperture 239.

Referring to FIG. 12, the lens actuator comprises different types ofelectrically controlled actuators. As shown the lens actuator comprisesan electrokinetic pump 746 a and electromechanical actuator 746 barranged in series. Providing one or more electrokinetic pumps in serieswith one or more electromechanical actuators is also useful. It isfurther understood that the same type of actuators need not be groupedtogether. Alternatively, as shown in FIG. 13, the lens actuator 245comprises at least one electrokinetic pump 846 a and at least oneelectromechanical actuator 846 b arranged in parallel with respect tothe lens aperture 239. Other arrangements of lens actuators are alsouseful.

The microlens chip can be provided with a fluid reservoir (not shown).Additionally, at least one inlet (not shown) is provided for filling thefluid system of the microlens chip. An outlet (not shown) may also befurther provided for facilitating flushing the system.

In one embodiment, the package 206 comprises bottom and top portions.The top portion comprises the aperture opening 239 while the bottomportion comprises the fluidic channel 240. In one embodiment, the topportion is formed from polymer or other materials that facilitateformation of the microlens. The bottom portion comprises a transparentmaterial, such as quartz, glass or a polymeric material. Forming thebottom section from a non-transparent material is also useful.

FIGS. 14 a-b show top and corresponding cross-sectional views of amicrolens chip 201 in accordance with one embodiment of the invention.As shown, the microlens comprises a package 206. In accordance with oneembodiment of the invention, the package comprises bottom and topportions 907 a-b. The top portion, which forms a top surface 209 of thepackage, includes an aperture opening 239 in which a microlens isformed.

In one embodiment, the top portion is formed from a hydrophobicmaterial. The top portion comprises, for example, a polymer. Varioustypes of polymers, such as polyimide, polydimethyl-siloxane (PDMS),polymethyl methacrylate (PMMA), polycarbonate, Nylon, and Teflon arealso useful. Other types of materials such as glass or quartz are alsouseful. A thin membrane can be provided over the top surface coveringthe lens aperture, as shown in FIG. 3. Providing a lens cover over thelens aperture, as shown in FIG. 4, is also useful.

The bottom portion includes a fluidic channel 240 in communication withthe lens aperture. In one embodiment, the bottom portion comprises anon-conductive material. Preferably, the non-conductive material istransparent. For example, the bottom portion can be formed from quartz.Other types of non-conductive transparent material, such as glass,polydimethyl-siloxane (PDMS), polymethyl methacrylate (PMMA),polycarbonate, Nylon and Teflon are also useful. Non-transparentmaterials, such as polyimide or ceramics are also useful to form thebottom portion.

The fluidic channel, in one embodiment, runs along the length L of thepackage. Providing a fluidic channel having other configurations is alsouseful. A fluid reservoir 964 can be located on the bottom portion incommunication with the fluidic channel. Locating the fluid reservoir inthe top portion or a combination of top and bottom portions is alsouseful. Preferably, the fluid reservoir is located at or near theopposite end of the fluidic channel as the lens aperture. Otherlocations for the fluid reservoir are also useful. The fluid reservoirprovides fluid in the channel for forming the microlens.

In one embodiment, an inlet 960 in communication with the fluidicchannel is provided to facilitate filling the lens package. In oneembodiment, the inlet is located toward a first end of the channel.Providing the inlet at other parts of the package is also useful. Anoutlet (not shown) may also be provided, for example, to facilitateflushing of the system.

The fluidic channel comprises an electrically controlled lens actuator245 for actuating the microlens. Other types of lens actuators are alsouseful. In one embodiment, the lens actuator is located between thefluid reservoir and aperture opening. In one embodiment, the lensactuator comprises an electroosmosis pump having a plurality ofmicrostructures 548 formed in the fluidic channel, creating a pluralityof micro-channels.

First and second electrodes 934 a-b are, for example, formed on an innersurface of the top portion of the package. Alternatively, the first andsecond electrodes may be formed on an inner surface of the bottomportion of the package. The electrodes are in communication with thefluidic channel. The electrodes are separated by the microstructures ofthe lens actuator. To provide access to the electrodes, the top portionis patterned to create electrode access windows 923 a-b. In oneembodiment, the electrodes comprise a conductive material, such aspalladium. Other types of metals (e.g., platinum, gold or alloysthereof), conductive polymers, conductive ceramics, conductive oxides(e.g., indium tin oxide), ionic liquid electrolytes or polymerelectrolytes are also useful. Focusing of the microlens can befacilitated by the use of a control unit (not shown), which controls theactuator by regulating the voltage applied to the electrodes.

Fabrication of the microlens can be achieved using microfabricationtechniques. For example, the various components, such as lens aperture,electrode windows, and inlet opening, of the top portion of the packageare formed by, for example, photolithography and micromachining inconjunction with standard techniques. Other techniques for forming theaperture and openings are also useful. For example, the aperture andopenings can be formed by laser machining or other machining techniques.In an alternative embodiment, the top portion is formed by moldingtechniques. The electrodes can be formed by depositing an electrodelayer on the inner surface of the top portion and patterned, as desired.

The various components of the bottom portion (e.g., fluid reservoir,fluidic channel and pump) can be formed using lithography and etchtechniques. For example, a mask is used to serve as an etch mask fordeep reactive ion etching (DRIE) to form the components. The bottomportion may also be formed using standard molding or machiningtechniques. After the top and bottom portions are formed, they areattached to complete the package. In one embodiment, the portions areattached using oxygen plasma activation. Other attachment processes,such as fusion bonding or polymer bonding, are also useful.

FIGS. 15 a-b show cross-sectional views of microlens chips 201 inaccordance with other embodiments of the invention. Referring to FIG. 15a, a microlens chip package 206 includes an electromechanical lensactuator 245. The electromechanical lens actuator changes the pressurein the fluidic channel 240 by causing a volume displacement of the fluidtherein. The change in pressure causes a microlens to be actuated at alens aperture 239.

In one embodiment, a fluid reservoir 1246 is provided in the fluidicchannel. Preferably, the fluid reservoir is relatively larger than thedimensions of the fluidic channel. The fluid reservoir is, for example,located at one end of the fluidic channel. Other locations for the fluidreservoir are also useful. In one embodiment, the reservoir comprises anoval or circular shape. Other geometric shapes are also useful.

In one embodiment, the lens actuator comprises a diaphragm 1255 incommunication with the fluidic channel. The diaphragm covers a surfaceof the fluidic channel. The diaphragm is located, for example, on a topsurface of the package. Locating the diaphragm at other parts of thepackage is also useful. The diaphragm can be formed as part of a portion1907 a of the package (e.g., lower or upper portion) by micromachiningtechniques, such as laser etching or molding. Such portion, for example,includes the other parts of the package, such as the fluidic channel.Alternatively, the diaphragm may be attached on the surface of the lenspackage or actuator housing 1257. Another portion 1907 b can be providedto seal the fluidic channel. The lens aperture can be located on eitherportion.

The diaphragm can be deflected in the V direction to cause a volumedisplacement of the fluid. For example, by deflecting the diaphragm, apressure is applied to the liquid in the fluidic channel. This in turncauses a volume displacement of the fluid in the channel, thus actuatingthe lens. For example, a volume displacement of the fluid in thepositive L direction can be effected by deflecting the diaphragm in thenegative V direction. Conversely, a volume displacement of the fluid inthe negative L direction can be achieved by deflecting the diaphragm inthe positive V direction.

The diaphragm can be formed from various types of materials. Forexample, the diaphragm can be formed from polymers such as polyethylene,polypropylene or polyimide. Other types of materials, such as Maylar,ceramics or pliable metals, are also useful. The thickness of thediaphragm should enable it to be deflected without breaking.

In one embodiment, an electromechanical stress inducer 1256 is providedin communication with the diaphragm. An electric field applied to thestress inducer to cause it to expand or contract in the V direction,controlling the stress induced on the diaphragm. The direction andmagnitude (e.g., amount of expansion or contraction) depends on themagnitude and polarity of the voltage or current applied. Thiseffectively causes a volume displacement of the fluid in the fluidicchannel to actuate the microlens.

In one embodiment, the stress inducer comprises a voice coil, such as alinear voice coil. The coil comprises a metal (e.g., copper, platinum,gold or aluminum) wire. Other types of wires are also useful. Othertypes of stress inducers, such as piezoelectric stress inducers, arealso useful.

In one embodiment, a housing 1257 is provided to encapsulate theelectromechanical stress inducer. The housing is, for example, attachedto the surface of the package. In one embodiment, the housing providesstructural support for the electromechanical stress inducer, enabling itto exert stress on the diaphragm. Various types of material, such aspolymeric or metallic materials, can be used to form the housing.

In one embodiment, the diaphragm is formed without inherent stress. Thisresults in the diaphragm having a relatively flat profile. As stress isexerted by the stress inducer, the diaphragm deflects in the negativedirection. As the electric field is reduced or removed, the diaphragmreverts to its natural profile.

In another embodiment, the diaphragm is formed with inherent stress,creating a bow shape. Preferably, the stress causes the diaphragm to bowupwards, forming a convex shape. Various techniques can be used toinduce inherent stress in the diaphragm, such as providing a stressinducing layer or varying the processing parameters used in forming thediaphragm. In the absence of an electric field (e.g., neutral position),the diaphragm naturally bows upward towards the stress inducer. Applyingan electric field to the stress inducer causes it to expand, deflectingthe diaphragm in the negative V direction. Providing inherent stress inthe diaphragm facilitates forming a concave or convex lens.Alternatively, the stress inducer is capable of causing the diaphragm todeflect in the positive and negative V direction to form either aconcave or convex lens. In yet another embodiment, the convex lens isformed when the diaphragm is in its natural or normal position.

Inlets and outlets may be provided to facilitate filling and flushing ofthe fluid system. To protect the microlens, a thin membrane or lenscover can be provided, as described in FIGS. 4 and 5. Providingadditional actuators, either of the same or different types, are alsouseful.

Referring to FIG. 15 b, the portion of the microlens package 206comprises a first and a second fluidic channels 240 a-b. In oneembodiment, the first fluidic channel includes a fluid reservoir 1246covered by a diaphragm 1255. The first and second fluidic channels areseparated by the lens reservoir. In one embodiment, the fluidic channelsand diaphragm are formed as part of a first portion (e.g., middleportion) of the package. Other techniques for providing the diaphragmand/or fluidic channels are also useful.

In one embodiment, a stress inducer 1256 is provided in communicationwith the diaphragm. The stress inducer exerts stress on the diaphragm tocause it to deflect, thereby changing the volume in the fluidicchannels. In one embodiment, the stress inducer 1256 is located incommunication with the diaphragm and in the second fluidic channel.Locating the stress inducer in other parts of the package, such as incommunication with the diaphragm and in the first fluidic channel, isalso useful. The stress inducer, for example, comprises a voice coil.Other types of electromechanical stress inducers are also useful.

A lens aperture 1239 is in communication with the first and secondfluidic channels in another portion of the package. The lens aperture ispreferably formed in the portion of the substrate which includes thechannels and diaphragm. Forming the lens aperture in other portions ofthe package is also useful. The first fluidic channel comprises a firstliquid and the second fluidic channel comprises a second liquid. Thefirst liquid, for example, serves to form the microlens. Forming themicrolens with the second liquid or by either the first or second liquidis also useful.

The fluids in the channels operate in a push-pull arrangement. Forexample, as the fluid in the first channel is displaced in the positiveL direction, the fluid in the second channel is displaced in thenegative L direction and vice-versa. In one embodiment, the lenscurvature radius is increased as the first fluid flows in the positive Ldirection. Conversely, the lens curvature radius is decreased by causingthe first fluid to flow in the negative L direction. Depending on theamount of flow in the negative L direction, a concave lens can beformed. Other configurations are also useful. Top and bottom portions,for example are attached to the middle portion to seal the channel toform the package.

In another embodiment, the package includes a fluidic channel and lensaperture. An external actuator is coupled to the package, causing fluidflow in the fluidic channel to actuate the microlens at the aperture. Inyet another embodiment, first and second lens concentric apertures areprovided in the package. Non-concentric apertures are also useful (ondifferent or same surfaces). The lens apertures are controlled by theexternal actuator. Providing each lens aperture with its own fluidicchannel and external actuator is also useful. Providing a plurality ofapertures which are located on one or both surfaces of the package andwhich are controlled by one or more actuators are also useful.

While the invention has been particularly shown and described withreference to various embodiments, it will be recognized by those skilledin the art that modifications and changes may be made to the presentinvention without departing from the spirit and scope thereof. The scopeof the invention should therefore be determined not with reference tothe above description but with reference to the appended claims alongwith their full scope of equivalents.

1. A variable focus microlens comprising: a microlens package; a cavityon the microlens package, the cavity forming a lens aperture; a fluidicchannel disposed in the microlens package, the fluidic channel is incommunication with the lens aperture; and an actuator integrated intothe microlens package in communication with the fluidic channel, whenfilled with a lens fluid the actuator causes the lens fluid to bulge atthe lens aperture to form a liquid lens and variably focusing the liquidlens by controlling fluid flow in the fluidic channel, the liquid lensdefining an air-liquid interface.
 2. The variable focus microlens ofclaim 1 wherein the liquid lens comprises a renewable liquid lens. 3.The variable focus microlens of claim 1 wherein the lens aperturecomprises any geometric shape, including a circular or rectangularshape.
 4. The variable focus microlens of claim 3 wherein the liquidlens comprises a renewable liquid lens.
 5. The variable focus microlensof claims 1-4 further comprising a protective lens cover covering thelens aperture.
 6. The variable focus microlens of claims 1-4 wherein thecavity forms first and second lens apertures on opposite surfaces of themicrolens package; and when filled with the lens fluid the actuatorcauses the lens fluid to bulge at the first and second lens apertures toform a biconvex or a biconcave liquid lens.
 7. The variable focusmicrolens of claim 6 further comprising first and second protective lenscover covering the first and second lens aperture.
 8. The variable focusmicrolens of claims 1-7 wherein the actuator comprises an electricallycontrolled actuator.
 9. The variable focus microlens of any of claims 8wherein the electrically controlled actuator comprises electrokineticpump or an electromechanical actuator.
 10. The variable focus microlensof claim 9 wherein the electromechanical actuator comprises: a fluidreservoir in communication with the fluidic channel; a diaphragmcovering the fluid reservoir; and an electrically controlled stressinducer in communication with the diaphragm, the electrically controlledstress inducer causes the diaphragm to deflect to control fluid flow inthe fluidic channel.
 11. The variable focus microlens of claim 10wherein the electrically controlled stress inducer comprises a voicecoil, micro-speaker, or piezoelectric stress inducer.
 12. The variablefocus microlens of claims 1-7 further comprising a second actuator. 13.The variable focus microlens of claim 12 where the first and secondactuators comprise electrically control actuators.
 14. The variablefocus microlens of claims 1-5 and 8-13 further comprising a secondaryfluidic channel in communication with the lens aperture, when filledwith a second fluid, the liquid lens when filled with the first fluidforms a liquid-liquid interface with the second fluid.
 15. The variablefocus microlens of claim 14 wherein the secondary fluidic channel andthe fluidic channel form a closed loop.
 16. The variable focus microlensof claims 6-13 further comprising secondary fluidic channels incommunication with the lens apertures, when filled with secondaryfluids, the liquid lenses when filled with the first fluid formsliquid-liquid interfaces with the secondary fluids.
 17. The variablefocus microlens of claim 16 wherein the secondary fluidic channels andthe fluidic channel form a closed loop.
 18. A variable focus microlenscomprising: a microlens package; first and second cavities on themicrolens package disposed in parallel, the first and second cavitiesforming first and second lens apertures a first fluidic channel disposedin the microlens package, the first fluidic channel is in communicationwith the first lens aperture; a second fluidic channel disposed in themicrolens package, the second fluidic channel is in communication withthe second lens aperture; a first actuator integrated into the microlenspackage in communication with the first fluidic channel, when the firstfluidic channel is filled with a fluid that forms a first liquid lens,the first actuator causes the lens fluid to bulge at the first lensaperture to form the first liquid lens and variably focusing the firstliquid lens by controlling fluid flow in the first fluidic channel; anda second actuator integrated into the microlens package in communicationwith the second fluidic channel, when the second fluidic channel isfilled with a lens fluid that forms a second liquid lens, the secondactuator causes the lens fluid to bulge at the second lens aperture toform the second liquid lens and variably focusing the second liquid lensby controlling fluid flow in the second fluidic channel.
 19. Thevariable focus microlens of claim 18 wherein the first and secondfluidic channels are isolated from each other by a separator.
 20. Thevariable focus microlens of claim 18-19 wherein the first and secondliquid lens comprise first and second renewable liquid lenses.
 21. Thevariable focus microlens of claim 18-19 wherein at least one of thefirst or second liquid lens comprises a renewable liquid lens.
 22. Thevariable focus microlens of claim 18-21 wherein the first and secondlens apertures comprise any geometric shape, including a circular orrectangular shape.
 23. The variable focus microlens of claims 18-22further comprising first and second protective lens covers covering thefirst and second lens apertures.
 24. The variable focus microlens ofclaims 18-22 further comprising at least one secondary fluidic channelin communication with one of the lens apertures, when filled with asecondary fluid, the liquid lens of the lens aperture in communicationwith the secondary fluidic channel forms a liquid-liquid interface withthe secondary fluid.
 25. The variable focus microlens of claim 24wherein the at least one secondary fluidic channel and the first orsecond fluidic channel form a closed loop.
 26. The variable focusmicrolens of claims 18-22 further comprising: first and second secondaryfluidic channels in communication with the first and second lensapertures, when filled with secondary fluids, the liquid lenses whenfilled with the first and second fluids form a liquid-liquid interfacewith the secondary fluids.
 27. The variable focus microlens of claim 26wherein the secondary fluidic channels and the fluidic channels formclosed loops.
 28. The variable microlens of claims 18-27 wherein theactuators comprise electrically controlled actuators.
 29. The variablefocus microlens of claim 28 wherein the electrically controlledactuators comprise electrokinetic pumps, electromechanical actuators orelectrokinetic pump and electromechanical actuator.
 30. The variablefocus microlens of claim 29 wherein the electromechanical actuatorcomprises; a fluid reservoir in communication with the fluidic channel;a diaphragm covering the fluid reservoir; and an electrically controlledstress inducer in communication with the diaphragm, the electricallycontrolled stress inducer causes the diaphragm to deflect to controlfluid flow in the fluidic channel.
 31. The variable focus microlens ofclaim 30 wherein the electrically controlled stress inducer comprises avoice coil, micro-speaker, or piezoelectric stress inducer.
 32. Thevariable focus microlens of claims 18-31 further comprising at least onesecondary actuator in communication with the first or second fluidicchannel.
 33. The variable focus microlens of claim 32 where thesecondary actuator comprise an electrokinetic pump.
 34. The variablefocus microlens of claims 18-31 further comprising secondary actuatorsin communication with the first and second fluidic channels.
 35. Thevariable focus microlens of claim 34 where the secondary actuatorscomprise electrokinetic pumps.
 36. A method of focusing a liquid lenscomprising: providing a fluidic channel containing a lens fluid in amicrolens package, the lens fluid having sufficient surface tension toform a liquid lens at an unsealed lens aperture on a surface of themicrolens package, the fluidic channel being in liquid communicationwith the lens aperture; providing an electrically controlled actuatorintegrated into the microlens package, wherein the actuator is incommunication with the fluidic channel; and applying a voltage orcurrent to the actuator to control fluidic pressure in the fluidicchannel to actuate the liquid lens at the lens aperture by changing thecurvature of the liquid lens.